You’ve got an old digital camera sitting around and you want to sell it online, but you have no idea how much to ask.

Chances are, you search eBay, Amazon and Craigslist to see what similar devices fetch. You scribble it all down on a notepad, do some rough math and come up with a ballpark figure. At best, it’s an educated guess.

If you think that sounds ridiculous, 15 years after the rise of online auctions and e-commerce, Tony Casparro and Fred Abler agree. That’s why the San Luis Obispo-based entrepreneurs co-founded Worth Monkey, an online service that tells you the fair market for electronics and a whole lot more.

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